You can use the same SecureBlackbox license to develop any number of products, provided that they all satisfy the requirements of the license itself. For example, if you hold an in-house license, you can develop as many products are you need, but they all need to satisfy the 'within the company' requirement.

We have an existing application. Let's name it Orange.
Now re-create a exactly the same application (rebranding), let's call it Banana .

These applications create output files, which are created using TElPGPWriter.
Lets name these as Orange.Org and Banana.Bnn for Orange and Banana applications respectively.

If we force to Open Banana.Bnn in Orange Application via changing the extension of Banana.Bnn to Banana.Org. The Orange Application will be able to do so, since it is already following the format of the files which the Orange application is configured to read.

Additionally, from our understanding the keys used to Encrypt and Decrypt the files are bundled with a license.

Now for the question, is there a to prevent the Orange and Banana Applications to open each other's generated files using a single license?

Additionally, from our understanding the keys used to Encrypt and Decrypt the files are bundled with a license.

Encryption keys are not related and/or bundled with a license used to activate SecureBlackbox components. These keys are usually generated by your code or some third-party application.

Quote

Now for the question, is there a to prevent the Orange and Banana Applications to open each other's generated files using a single license?

As TElPGPWriter generates OpenPGP compatible files, any OpenPGP compliant software will be able to open them including two versions of your application. If you want to bind these files to your applications you can use additional built in encryption keys or something like that, but this will be a simple protection that may be broken by experienced specialist.